<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">

function a(){
	//var c = 10;
	//var c = 10;
	//window.b = c;
	//window.d = b;
	//var c = b = d = 5;
};
a();
alert(b);//5
alert(d);//5
alert(c);//x


</script>
</body>
</html>